A Syrian gunman shoots on the air during Thursday's funeral of 29 year-old Free Syrian Army fighter, Husain Al-Ali, who was killed during clashes in Aleppo, in the town of Marea on the outskirts of Aleppo city, Syria, (ASSOCIATED PRESS / Khalil Hamra)

AZAZ, Syria (AP) — Syrian rebels were running low on ammunition and guns Friday as government forces tried to consolidate their control over Aleppo, the country's largest city and a deadly battleground for more than two weeks.

The seemingly intractable, 17-month-old conflict in Syria has defied all international attempts to calm the bloodshed. Rebels and activists said Friday they have had enough of diplomacy and appealed to the international community to send weapons.

"The warplanes and helicopters are killing us. They're up there in the sky 15 hours a day," said Mohammad al-Hassan, an activist in Aleppo's Salaheddine district, the main rebel stronghold in the city.

"It's warplanes against Kalashnikovs, tanks fighting against rifles," he said. "I don't know how long this situation can be sustained."

As Syrian soldiers bombarded rebel positions in Aleppo from the ground and air, diplomats said former Algerian foreign affairs minister and longtime U.N. official Lakhdar Brahimi has emerged as a strong candidate to replace Kofi Annan as U.N. peace envoy to Syria.

Annan announced his resignation last week, ending a frustrating six-month effort that failed to achieve even a temporary cease-fire as the country descended into civil war. Activists say some 20,000 people have been killed.

Also Friday, the U.S. announced sanctions on Hezbollah for providing support to Syrian President Bashar Assad's regime — a symbolic move, as Washington already has designated the Lebanese militant group a terrorist organization.

Still, the sanctions emphasized how Syria's alliance with Hezbollah — and with the group's patrons in Iran — means the conflict has the potential to escalate dramatically.

In one sign of how the conflict can drag in Lebanon, rebels in the town of Azaz are holding 11 Lebanese Shiite pilgrims seized on a road nearby months ago.

The head of the Azaz rebels' Political Office, Samir Hajj Omar, said Friday the prisoners would be released only if Hezbollah chief Hassan Nasrallah apologizes to the Syrian people for supporting Assad.

"He has been brutal against the Syrian revolution and the Syrian people in his speeches, so we just want an apology from him," he said in an interview in Azaz, about 35 kilometers (22 miles) northwest of Aleppo by the Turkish border.

He said interrogations by rebels had revealed that four of the prisoners are connected to Hezbollah and one is related to Nasrallah. Those claims could not be independently verified.

Mohammed Nour, head of the town's media office, said rebels had stopped their bus nearby and let the women traveling with them go. Nour initially said some of the men were found to have Hezbollah ID cards. Hezbollah is very secretive about who plays a military role in the organization and does not issue ID cards.

Later, Nour said, the rebels realized that the men were indeed pilgrims returning from Iran, as they had claimed.

Asked what the men had done wrong to merit being detained for so long, Omar said it was payback over "Nasrallah's loyalty to the Syrian regime."

"What did the Syrian people do wrong?" he said.

The relentless violence triggered a fresh wave of civilians streaming across the border into neighboring Turkey. Turkish officials said more than 1,500 Syrians arrived over the past 24 hours, increasing the number of refugees in Turkey to about 51,500.

Rebels control several border crossings into Turkey. At least one of them, Bab al-Salama, near Azaz, is operating normally, with Turkish officials on the other side stamping passports for people passing into Syria.

The regime has been trying for more than two weeks to drive rebels out of Aleppo, which has a population of about 3 million. The state news agency claimed Wednesday that Assad's forces had regained control of the Salaheddine neighborhood, the main rebel area in Aleppo. But activists said rebels were still putting up a fight there on Friday despite being low on ammunition.

Aleppo holds great symbolic and strategic importance. Some 40 kilometers (25 miles) from the Turkish border, it has been a pillar of regime support during the uprising against the Assad regime. An opposition victory there would allow easier access for weapons and fighters from Turkey, where many rebels are based.

An Aleppo-based activist said government forces were shelling rebel-controlled areas in the southwestern part of Aleppo and in the northeast. Towns and villages in Aleppo suburbs were "at the mercy" of fighter jets and helicopters strafing the area, he said.

"Soon there will be nothing left to destroy in Aleppo. ... The regime is using air power without shame," he said, asking that his name not be used out of fear for his personal safety.

Protesters across many parts of the country rallied after midday prayers Friday, urging the international community to arm the opposition fighters.

"Give us anti-aircraft guns. Where is your conscience?" read a small poster held by a protester in the village of Kfar Zeita in the central Hama province.

But there has been deep reluctance to openly arm the fighters, out of fears that it could escalate the violence and because the rebel Free Syrian Army is not a unified group. Many rebel groups operate largely independently of each other, in many cases sharing only the goal of toppling Assad.

On Friday, Britain's government said it is giving an extra 5 million pounds (US$7.8 million) worth of aid — but no weapons — to Syria's opposition.

Foreign Secretary William Hague said the funds would pay for items including satellite phones, power generators and medical kits.

Britain has previously given 1.4 million pounds (US$2.2 million) worth of nonlethal support to Syria's opposition. The United States has earmarked a fund of $25 million to spend on nonlethal communications assistance.

The activists, from the Britain-based Syrian Observatory for Human Rights as well as Syria's Local Coordination Committees, also reported shelling Friday of several areas just outside Damascus, where rebels also were active. Residents reported hearing loud blasts in Damascus from the shelling on the outer edges of the city, the activists said.